Security capability negotiation method, system, and equipment

ABSTRACT

A security capability negotiation method is provided that is applicable to perform security capability negotiation during a mobile network handover. Moreover, a security capability negotiation system is also provided. Consistent with the provided system and method, it may be unnecessary for the MME to know the security capability of the corresponding eNB in a certain manner during a handover from a 2G/3G network to an LTE network. Meanwhile, during the handover from the LTE network to the 3G network, the SGSN does not need to introduce new requirements.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 15/495,607, filed on Apr. 24, 2017, now U.S. Pat. No. 10,383,017, which is a continuation of U.S. patent application Ser. No. 14/298,341, filed on Jun. 6, 2014, now U.S. Pat. No. 9,668,182, which is a continuation of U.S. patent application Ser. No. 12/503,942, filed on Jul. 16, 2009, now U.S. Pat. No. 8,774,759, which is a continuation of International Patent Application No. PCT/CN2008/070880, filed on May 5, 2008. The International Patent Application claims priority to Chinese Patent Application No. 200710074333.9 filed on May 8, 2007. All of the afore-mentioned patent applications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present disclosure relate to the field of communications, and more particularly to a security capability negotiation method, system, and equipment.

BACKGROUND

Referring to FIG. 1, an existing 3^(rd) Generation Partnership Project (3GPP) radio network is divided into a 3GPP radio access network (RAN) and a core network (CN).

The 3GPP RAN is further classified into three types as follows.

GSM edge radio access network (GERAN): 2G/2.5G access network, collectively referred to as 2G access network below, and including a base transceiver station (BTS) and a base station controller (BSC).

Universal terrestrial radio access network (UTRAN): 3G access network, including a node B (NodeB) and a radio network controller (RNC).

Evolved UMTS terrestrial radio access network (EUTRAN): also known as future long term evolution (LTE) access network, including an evolved node B (eNodeB, and eNB for short below).

The above three RANs are all configured to implement functions related to radio services, and meanwhile realize security capability negotiation with terminals.

A 2G/3G core network is further divided into a circuit-switched (CS) domain and a packet-switched (PS) domain. For ease of illustration, CS-related entities are omitted, and only the PS domain remains. The PS domain performs data service exchange and routing with external packet-based networks beforehand, and includes a serving GPRS support node (SGSN) and a gateway GPRS support node (GGSN). The SGSN is mainly configured to realize route-forwarding, mobility management, session management, and user authentication, and the GGSN is mainly configured to realize the connection with the external packet-based networks, and also implement data transmission on the user plane.

A future evolved core network is also referred to as a system architecture evolution (SAE), including entities such as a mobility management entity (MME) and SAE gateway (SAE GW)/packet data network gateway (PDN GW)/home subscriber server (HSS). Similar to the SGSN, the MME is mainly configured to realize mobility management and user authentication. The SAE GW/PDN GW serves as anchor points on the user plane between different access systems. The HSS is mainly configured to store user subscription data.

In the 2G network, the SGSN performs the security capability algorithm negotiation between the signaling plane and the user plane. In the 3G network, the RNC performs the security capability algorithm negotiation between the signaling plane and the user plane. In the evolved network LTE/SAE, as the RNC/SGSN does not exist, the MME performs the non-access signaling (NAS) algorithm negotiation, and the eNB performs the radio resource control (RRC)/user plane (UP) algorithm negotiation.

When a user is handed over from a 2G/3G network (2G/3G) to an LTE network, or from an LTE to a 2G/3G network, as the entities responsible for the security capability negotiation change and the security capabilities thereof may be different, the security capability negotiation needs to be re-performed. Here, the security capability negotiation means encryption algorithm for the 2G network, means integrity protection algorithm and encryption algorithm for the 3G network, and means NAS algorithm (encryption algorithm and integrity protection algorithm), RRC algorithm (encryption algorithm and integrity protection algorithm), and UP algorithm (encryption algorithm) for the LTE network.

Particularly, during the handover from the LTE network to the 2G/3G network, a user equipment (UE) sends its own GERAN (encryption algorithm)/UTRAN security capability (encryption algorithm and integrity protection algorithm) carried in an initial Layer 3 message to the MME. The MME then sends the capabilities of the UE to the SGSN. The SGSN selects and sends the corresponding GERAN/UTRAN security capability algorithm to the UE through the MME. During the handover from the LTE to 2G, the SGSN selects the security capability algorithm. However, during the handover from the LTE to 3G, according to the above description about the 3G network, the RNC, instead of the SGSN, selects the security capability algorithm; otherwise, the SGSN has to introduce a new requirement of selecting the security capability algorithm. Meanwhile, the SGSN must know the security capability of the RNC in a certain manner, and then sends the selected algorithm to the RNC, so that additional interaction between the SGSN and the RNC needs to be constructed.

During the handover from the 2G/3G to the LTE, the SGSN queries the UE for the NAS (encryption algorithm and integrity protection algorithm)/UP (encryption algorithm)/RRC (encryption algorithm and integrity protection algorithm) security capability. During the handover from the 2G/3G to the LTE, the SGSN sends the capabilities of the UE to the MME. Then, the MME selects and sends all the NAS/RRC/UP security capability algorithms to the UE through the SGSN.

In the implementation of the present invention, it is found in the prior art that, as the MME selects all the NAS/RRC/UP security capability algorithms, the MME must know the security capability of the corresponding eNB in a certain manner (for example, by configuring or extending interactive messages with the eNB), thus resulting in an inflexible configuration and a complicated process flow.

SUMMARY

Embodiments of the present disclosure are directed to a security capability negotiation method, system, and equipment, so as to facilitate the security capability negotiation during the network handover.

In an embodiment of the present disclosure, a security capability negotiation method is provided, which is applicable to perform security capability negotiation during a mobile network handover. The method includes the following process:

A second network receives a handover request sent by a first network.

An access network entity of the second network selects a corresponding security capability, or an access network entity and a core network (CN) entity of the second network respectively select a corresponding security capability.

The second network sends the selected security capability to a User Equipment (UE) via the first network.

Consistent with an embodiment of the present disclosure, a security capability negotiation system is provided, which is applicable to perform security capability negotiation during a mobile network handover. The system includes an access network entity and a core network entity of a first network, and an access network entity and a core network entity of a second network.

The access network entity of the second network is configured to select a corresponding security capability when the first network requests to hand over to the second network.

The core network entity of the second network is configured to select a corresponding security capability together with the access network entity of the second network when the first network requests for handing over to the second network.

The core network entity and the access network entity of the first network are configured to send the security capabilities selected by the second network to a user equipment (UE).

Consistent with an embodiment of the present disclosure, a network including an access network entity and a core network entity is further provided.

The access network entity is configured to receive a handover request sent by a peer-end network.

The core network entity is configured to select and send a corresponding security capability to the UE via the peer-end network together with the access network entity of the network when the peer-end network requests to hand over to the current network.

The embodiments of the present disclosure provide at least the following effects. During the handover from the 2G/3G to the LTE network, the MME and the eNB respectively implement the negotiation of the NAS security algorithm and the RRC/UP security algorithm, so that it is unnecessary for the MME to know the security capability of the corresponding eNB in a certain manner (for example, by configuring or extending interactive messages with the eNB). Meanwhile, during the handover from the LTE network to the 3G network, a new requirement for the SGSN is avoided, and the interaction between the SGSN and the RNC is also unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view of a conventional 3GPP radio network.

FIG. 2 is a flow chart illustrating a security capability negotiation method during the handover from a 2G/3G network to an LTE network according to a first embodiment of the present disclosure.

FIG. 3 is a flow chart illustrating a security capability negotiation method during the handover from an LTE network to a 3G network according to a second embodiment the present disclosure.

FIG. 4 is a schematic structural view illustrating a security capability negotiation system according to a third embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure are illustrated in detail below with reference to the accompanying drawings.

Referring to FIG. 2, the security capability negotiation method according to the first embodiment includes the following processes.

In this embodiment, the UE is handed over from 2G/3G to the LTE. First, it is assumed that a UE accesses services via a 2G/3G access network (2G/3G Access).

In process 201, the 2G/3G access network determines to initiate a handover.

In process 202, the 2G/3G access network initiates a handover request message to the SGSN.

In process 203, the SGSN initiates a handover preparation request message to the MME. The handover preparation request message carries various security capability sets supported by the UE, including at least one NAS algorithm (encryption algorithm and integrity protection algorithm), at least one RRC algorithm (encryption algorithm and integrity protection algorithm), and at least one UP algorithm (encryption algorithm).

Here, the SGSN may obtain the security capability sets supported by the UE in the following methods.

The SGSN directly requests the UE to send the security capability sets supported thereby.

A 2G/3G access network entity (BSS or RNC) first determines to initiate a handover, then requests the UE for the security capability sets supported thereby, and sends the capability sets to the SGSN in process 202.

In process 204, the MME selects a NAS algorithm (encryption algorithm and integrity protection algorithm) according to the UE supported NAS algorithm (encryption algorithm and integrity protection algorithm), the system allowable NAS algorithm (encryption algorithm and integrity protection algorithm), together with the NAS algorithm (encryption algorithm and integrity protection algorithm) supported by the MME itself.

It should be noted that, as the UE supported NAS algorithm (encryption algorithm and integrity protection algorithm), the system allowable NAS algorithm (encryption algorithm and integrity protection algorithm), and the NAS algorithm (encryption algorithm and integrity protection algorithm) supported by the MME itself are all various, the selected NAS algorithm (encryption algorithm and integrity protection algorithm) is a NAS algorithm (encryption algorithm and integrity protection algorithm) supported by all the UE, the system and the MME.

In process 205, the MME sends a handover preparation request message to the eNB. The handover preparation request message carries at least one RRC algorithm (encryption algorithm and integrity protection algorithm) supported by the UE and at least one UP algorithm (encryption algorithm) supported by the UE, and may also carry at least one RRC algorithm (encryption algorithm and integrity protection algorithm) allowed by the system and at least one UP algorithm (encryption algorithm) allowed by the system.

In process 206, a bearer resource between the eNB and the MME is established, including the establishment of a radio resource.

In process 207, the eNB selects an RRC algorithm (encryption algorithm and integrity protection algorithm) and a UP algorithm (encryption algorithm) according to the at least one RRC algorithm (encryption algorithm and integrity protection algorithm) and the at least one UP algorithm (encryption algorithm) that are supported by the UE, together with the RRC security capability sets (encryption algorithm and integrity protection algorithm) and UP security capability sets (encryption algorithm) that are supported by the eNB itself.

It should be noted that, as the RRC algorithms (encryption algorithm and integrity protection algorithm) and UP algorithms (encryption algorithm) that are supported by the UE, the RRC algorithms (encryption algorithm and integrity protection algorithm) and UP algorithms (encryption algorithm) that are allowed by the system, and the RRC algorithms (encryption algorithm and integrity protection algorithm) and UP algorithms (encryption algorithm) that are supported by the eNB are various, the selection here means selecting an RRC algorithm (encryption algorithm and integrity protection algorithm) and UP algorithm (encryption algorithm) which are both supported by the UE and the eNB.

In process 205, if the handover preparation request message sent by the MME to the eNB also carries at least one RRC algorithm (encryption algorithm and integrity protection algorithm) and at least one UP algorithm (encryption algorithm) that are allowed by the system, the eNB may further select the RRC algorithm (encryption algorithm and integrity protection algorithm) and UP algorithm (encryption algorithm) which are supported by all the UE, the eNB and the system based on the at least one RRC algorithm (encryption algorithm and integrity protection algorithm) and the at least one UP algorithm (encryption algorithm) that are allowed by the system.

In process 208, the eNB sends a handover preparation acknowledgement message to the MME. The handover preparation acknowledgement message carries the selected RRC algorithm (encryption algorithm and integrity protection algorithm) and the selected UP algorithm (encryption algorithm).

In process 209, the MME sends a handover preparation acknowledgement message to the SGSN. The handover preparation acknowledgement message carries the selected NAS algorithm (encryption algorithm and integrity protection algorithm), the selected RRC algorithm (encryption algorithm and integrity protection algorithm), and the selected UP algorithm (encryption algorithm).

In processes 210 to 211, the SGSN sends a handover command message to the UE via the 2G/3G access network, for indicating the UE to hand over to a destination network. The handover command message carries the selected NAS algorithm (encryption algorithm and integrity protection algorithm), the selected RRC algorithm (encryption algorithm and integrity protection algorithm), and the selected UP algorithm (encryption algorithm).

In process 212, the subsequent handover process is implemented.

Thereby, the security capability negotiation between the UE and the network equipment (eNB/MME) is completed.

Process 204 may also be performed between processes 205 and 209. Process 207 may also be performed before process 206.

In this embodiment, during the handover from the 2G/3G to the LTE network, the NAS algorithm protection is implemented between the UE and the MME, the RRC/UP algorithm protection is implemented between the UE and the eNB, and the MME and the eNB are respectively configured to realize the negotiation of the NAS security algorithm and the RRC/UP security algorithm, so that it is unnecessary for the MME to know the security capability of the corresponding eNB in a certain manner (for example, by configuring or extending interactive messages with the eNB) as in the prior art.

Referring to FIG. 3, in a second embodiment of the present disclosure, a security capability negotiation method includes the following processes.

In this embodiment, a UE hands over from an LTE to 3G. First, it is assumed that a UE accesses services via an LTE access network (eNB).

In process 301, the eNB determines to initiate a handover.

In process 302, the eNB initiates a handover request message to the MME.

In process 303, the MME initiates a handover preparation request message to the SGSN. The handover preparation request message carries 3G security capability sets supported by the UE, including encryption algorithm and integrity protection algorithm.

Here, the MME may obtain the 3G security capability sets supported by the UE in the following methods.

Before the handover, an initial Layer 3 message already carries the 3G security capability sets supported by the UE, and the UE sends the capability sets to the MME.

The MME directly requests the UE to send the 3G security capability sets supported by the UE.

The eNB first determines to initiate a handover, then requests the UE for the 3G security capability sets supported by the UE, and sends the capability sets to the MME in process 302.

In process 304, the SGSN sends a handover preparation request message to the 3G access network (RNC). The handover preparation request message carries the 3G security capability sets supported by the UE. The 3G security capability sets supported by the UE includes encryption algorithm and integrity protection algorithm, and the handover preparation request may also carry the system allowable 3G security capability sets.

In process 305, a bearer resource between the 3G access network (RNC) and the SGSN is established, including the establishment of a radio resource.

In process 306, the 3G access network (RNC) selects the 3G security capability sets according to the 3G security capability sets supported by the UE together with the 3G security capability sets supported by the 3G access network itself.

It should be noted that, as the 3G security capability sets supported by the UE and the 3G security capability sets supported by the 3G access network (RNC) itself are various, the selection here means selecting the 3G security capability sets supported by the UE and the 3G access network (encryption algorithm and integrity protection algorithm) from the above two categories of 3G security capability sets.

In process 304, if the handover preparation request message sent by the SGSN to the 3G access network (RNC) also carries the system allowable 3G security capability sets, the 3G access network (RNC) may further combine the system allowable 3G security capability sets to select the 3G security capability sets.

In process 307, the 3G access network (RNC) sends a handover preparation acknowledgement message to the SGSN. The handover preparation acknowledgement message carries the selected 3G security capability sets.

In process 308, the SGSN sends a handover preparation acknowledgement message to the MME. The handover preparation acknowledgement message carries the selected 3G security capability sets.

In processes 309 to 310, the MME sends a handover command message to the UE via the eNB, indicating the UE to hand over to a destination network. The message carries the selected 3G security capability sets.

In process 311, the subsequent handover process is implemented.

Thereby, the security capability negotiation between the UE and the network equipment (RNC) is completed.

Process 306 may also be performed before process 305.

In this embodiment, the SGSN does not need to introduce new requirements during the handover from the LTE to the 3G network.

Referring to FIG. 4, in a third embodiment of the present disclosure, a security capability negotiation system is provided, which is applicable to perform security capability negotiation during a mobile network handover. The system includes an access network entity 401 and a core network entity 402 of a first network, and an access network entity 403 and a core network entity 404 of a second network. The access network entity 403 of the second network is configured to select a corresponding security capability when the first network requests to be handed over to the second network. The core network entity 404 of the second network is configured to select a corresponding security capability together with the access network entity 403 of the second network when the first network requests to be handed over to the second network. The core network entity 402 and the access network entity 401 of the first network are configured to send the security capabilities selected by the second network to a UE 405.

In this embodiment, a network including an access network entity and a CN entity is further provided. The access network entity is configured to receive a handover request sent by a peer-end network. The CN entity is configured to select and send a corresponding security capability to the UE via the peer-end network together with the access network entity of the network when the peer-end network requests to be handed over to the current network.

When the UE hands over from the 2G/3G network to the LTE network, the first network is a 2G network or a 3G network, the access network entity of the 2G network includes a BTS and a BSC. The access network entity of the 3G network includes a node (NodeB) and an RNC. The core network entity of the 2G/3G network includes an SGSN. The second network is an LTE RAN, the access network entity thereof is an evolved node (eNodeB), and the core network entity thereof is an MME. The security capability includes NAS integrity protection and encryption algorithm, RRC integrity protection and encryption algorithm, and UP encryption algorithm. The MME is configured to select the NAS integrity protection and encryption algorithm, and the eNodeB is configured to select the RRC integrity protection, encryption algorithm, and UP encryption algorithm. The working principle and process are shown in FIG. 2, and the details will not be repeated herein. The MME and the eNB are adopted to realize the negotiation of the NAS security algorithm and the RRC/UP security algorithm respectively, so that it is unnecessary for the MME to know the security capability of the corresponding eNB in a certain manner (for example, by configuring or extending interactive messages with the eNB) as in the prior art.

When the UE hands over from the LTE network to the 3G network, the access network entity of the first network is eNodeB, the core network entity of the first network is MME, the access network entity of the second network is RNC, and the core network entity of the second network is SGSN. The security capability includes 3G security capability sets, and the 3G security capability sets further include encryption algorithm and integrity protection algorithm. The working principle and process are shown in FIG. 2, and the details will not be repeated herein. The RNC is configured to select the 3G security capability sets, so that the SGSN does not need to introduce new requirements during the handover from the LTE to the 3G network, and the interaction between the SGSN and the RNC is also unnecessary.

Through the above description of the embodiments, it is apparent to those skilled in the art that the embodiments may be accomplished by software on a necessary universal hardware platform, and definitely may also be accomplished by hardware. Therefore, some embodiments of the present disclosure can be substantially embodied in the form of a software product. The software product may be stored in a non-volatile storage medium such as a CD-ROM, USB disk, or removable hard disk, and contains several instructions to indicate a communication equipment (for example, a personal computer, server, or network equipment) to perform the method as described in the embodiments of the present disclosure.

It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosed embodiments cover modifications and variations thereof provided that they fall within the scope of the following claims and their equivalents. 

What is claimed is:
 1. A method implemented during a handover of a user equipment (UE) from a first network to a second network, the method comprising: sending, by a core network (CN) entity of the second network to an access network entity of the second network, at least one radio resource control (RRC) algorithm and at least one user plane (UP) algorithm that are supported by the UE; selecting, by the access network entity of the second network, based on the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, an RRC algorithm and an UP algorithm supported by both the UE and the access network entity of the second network; and sending, by the access network entity of the second network, the selected RRC algorithm and the selected UP algorithm to the CN entity of the second network.
 2. The method according to claim 1, further comprising: sending, by the CN entity of the second network, the selected RRC algorithm and the selected UP algorithm to a CN entity of the first network.
 3. The method according to claim 2, further comprising: sending, by the CN entity of the first network, the selected RRC algorithm and the selected UP algorithm to an access network entity of the first network.
 4. The method according to claim 3, further comprising: sending, by the access network entity of the first network, the selected RRC algorithm and the selected UP algorithm to the UE.
 5. The method according to claim 1, wherein before sending the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, the method comprises: receiving, by the CN entity of the second network, from a CN entity of the first network, the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE.
 6. The method according to claim 5, further comprising: receiving, by the CN entity of the second network, from the CN entity of the first network, at least one Non-Access signaling (NAS) algorithm supported by the UE; and selecting, by the CN entity of the second network, a NAS algorithm supported by both the UE and the CN entity of the second network, according to the at least one NAS algorithm supported by the UE and at least one NAS algorithm supported by the CN entity of the second network.
 7. The method according to claim 1, wherein a radio access technology of the first network is different from a radio access technology of the second network.
 8. The method according to claim 1, wherein the selected RRC algorithm and the selected UP algorithm are selected from the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, and at least one RRC algorithm and at least one UP algorithm that are supported by the access network entity of the second network.
 9. A communications system comprising: an access network entity and a core network (CN) entity, wherein the communications system functions as a second network during a handover of a user equipment (UE) from a first network to the second network, wherein the CN entity is configured to send at least one radio resource control (RRC) algorithm and at least one user plane (UP) algorithm that are supported by the UE to the access network entity, and the access network entity is configured to: receive the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE from the CN entity; select, based on the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, an RRC algorithm and an UP algorithm supported by both the UE and the access network entity; and send the selected RRC algorithm and the selected UP algorithm to the CN entity.
 10. The communications system according to claim 9, wherein the CN entity of the second network is configured to send the selected RRC algorithm and the selected UP algorithm to a CN entity of the first network.
 11. The communications system according to claim 9, wherein the CN entity of the second network is configured to receive from a CN entity of the first network, the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE.
 12. The communications system according to claim 9, wherein the CN entity of the second network is configured to: receive from the CN entity of the first network, at least one non-access signaling (NAS) algorithm supported by the UE; select, based on the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, an NAS algorithm supported by both the UE and the CN entity of the second network; and send the selected NAS algorithm together with the selected RRC algorithm and the selected UP algorithm to the CN entity of the first network.
 13. The communications system according to claim 9, wherein a radio access technology of the first network is different from a radio access technology of the second network.
 14. The communications system according to claim 9, wherein the selected RRC algorithm and the selected UP algorithm are selected from the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, and at least one RRC algorithm and at least one UP algorithm that are supported by the access network entity of the second network.
 15. A communications system comprising: a first network and a second network, wherein the first network comprises a first access network entity and a first core network (CN) entity, and the second network comprises a second access network entity and a second CN entity, and wherein during a handover of a user equipment (UE) from the first network to the second network, the second CN entity is configured to send at least one radio resource control (RRC) algorithm and at least one user plane (UP) algorithm that are supported by the UE to the second access network entity; and the second access network entity is configured to: receive the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE from the second CN entity; select, based on the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, an RRC algorithm and an UP algorithm supported by both the UE and the access network entity; and send the selected RRC algorithm and the selected UP algorithm to the second CN entity.
 16. The communications system according to claim 15, wherein the second CN entity is configured to send the selected RRC algorithm and the selected UP algorithm to the first CN entity.
 17. The communications system according to claim 16, wherein the first CN entity is configured to receive the selected RRC algorithm and the selected UP algorithm from the second CN entity, and send the selected RRC algorithm and the selected UP algorithm to the first access network entity of the first network.
 18. The communications system according to claim 17, wherein the first access network entity is configured to send the selected RRC algorithm and the selected UP algorithm to the UE.
 19. The communications system according to claim 15, wherein the second CN entity is configured to receive from the first CN entity, the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE.
 20. The communications system according to claim 15, wherein the second CN entity is configured to: receive from the first CN entity, at least one non-access signaling (NAS) algorithm supported by the UE; select, based on the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, an NAS algorithm supported by both the UE and the second CN entity; and send the selected NAS algorithm together with the selected RRC algorithm and the selected UP algorithm to the first CN entity.
 21. The communications system according to claim 15, wherein a radio access technology of the first network is different from a radio access technology of the second network.
 22. The communications system according to claim 15, wherein the selected RRC algorithm and the selected UP algorithm are selected from the at least one RRC algorithm and the at least one UP algorithm that are supported by the UE, and at least one RRC algorithm and at least one UP algorithm that are supported by the second access network entity. 